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Thread: Polo 6R braking thread (Mainly GTI/Diesel)

  1. #11
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    i too can vouch for the 'Control module 03, 10 Adaptation, 09: 0, 1, 2' modification... i had quattro set it to '2 (hard)' and the difference is amazing... a definite must for any 6r gti owner!

    josh
    2012 Volkswagen Polo GTI (Shadow Blue) | Current Upgrades - APR Stage 2 Tune | Yokohama ADVAN Neova AD08Rs | HP Cold Air Intake | OKADA Plasma Direct Coil Packs | HP Turboback Exhaust | HP DQ200 Tune | Tarox 6-Pot 323mm Front Brakes | Whiteline Rear Sway Bar | Uprated Engine Mounts Planned Upgrades - | Coil Overs | HP Intercooler |

  2. #12
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    Using the Porsche 997 and Ferrari F1 Brembo setuos as examples of drilled or slotted rotors being useless is highly misleading. For carbon ceramic setups like these, where the braking effect is almost entirely due to abrasive friction and the rotors and pads operate efficiently (and only efficiently) at very high temperatures, this is true. Also, these cars have efficient ducting to air to the rotors designed into their body work unlike the vast majority of cars on the road.

    While the amount of outgassing from modern pad compounds is insignificant, the vast majority of cars run a iron rotor/non-ceramic pad combination and these work through both abrasive and adherent friction where there is a continual transfer of material from the pads to the rotors (this is why brake pads need bedding in, especially with a change in pad compound). With these, under heavy braking loads, the pad dust from the abrasive friction can prevent further transfer of pad material to the rotors, reducing the adherent friction component which lowers the overall braking power. Slots and holes give the dust somewhere to go, helping maintain the braking power in these extreme situations. Holes are better at passing the dust slots can fill and they also improve ventilation, reducing rotor temperatures, further maintaining braking efficiency under heavy loads and reducing pad taper although cracks can develop from the holes - this tendency can be greatly reduced with peening of the holes but no one does it as it would reduce rotor sales.

    We are talking about braking at levels that shouldn't be experienced on public roads, even by manic heroes. For road use, normal ventilated rotors should be all that is necessary. And I seriously doubt that a properly driven and maintained Polo would experience pad or fluid fade with stock rotors except on a race track.

    I fully agree about the confusion between braking sensitivity and power - the brakes on MkVI Golfs are too grabby yet people who don't have a clue think this is due to the brakes just being more powerful. If anyone knows the adaptation to reduce the sensitivity on a MkVI Golf, please pass on the info!

    Scotty, come for a drive with me or let me take you for a drive in your car (do this before you judge me as being 'snooty' - getting this old has taught me a few things).
    Last edited by kaanage; 24-03-2012 at 01:02 AM.
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  3. #13
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    The point being made Greg is that cross drilled rotors are pointless for road going vehicles, regardless of if they're steel or carbon ceramic. The words I speak are directly from the mouth of the Porsche design team and high percentage of race cars around the world run some form of slotted rather than drilled rotors. I stand by my statement as do the 5 engineers in my office that have worked for race teams around the world.

    In regards to the adherent vs abrasive friction on rotors, I will cover this when I have more time.

    In regards to your last point though, as I have said before, the very first week I owned this car I had brake fade, so I did something about it and have not had it since.

    We got the Win for DQ200. Now come to the party VGA on DQ250 and DQ500 issues. You know they're there.
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  4. #14
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    Gavs,

    The owner of a 6r polo gti was having some issues with voltage / battery / car not starting and I was taking a look to save the trip to the dealer as I work with them. Turns out it was a faulty battery - temporary battery in place - all fixed.

    Anyway, while I was there, I remembered your 'the pedal isn't connected to the master cylinder'. From where I can stand, the foot pedal is indeed connected to the master cylinder directly, and the pedal itself has electronic position sensing on it but is connected to the main master cylinder which allows the master cylinder vaccum assist level to be adjusted base on the input / module settings.

    Based on your assertion earlier Gavs, if the pedal is not connected in any way to the master cylinder, the experience I should have when no engine is running and no battery is connected is the brakes do not work at all (which would never, ever, ever pass safety standards just fyi).

    So, I removed the battery, drained the system entirely of power and on the top of a hill, rolled down it without any assisting. Low and behold, the first few presses, residual vacuum in the system assisted the brakes once, maybe twice, then it was all up to my to exert/pump the master cyl to apply pressure to the brakes. It wasn't brilliant, but it worked.

    /2c.

  5. #15
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    Quote Originally Posted by gavs View Post
    In the 6R, your braking system is 90% identical to any hydraulic braking system except for one thing, the brake pedal itself. It is not connected to the braking system
    I was worried by this revelation too. AFIK, no recent 4 wheel passenger vehicle (1960's Citroen ID/DS models aside) doesn't have the brake pedal physically connected to the hydraulics, whatever the electronic/vacuum assistance hung on in between. But I'm happy to be corrected.

    Otherwise, a very good write-up.

  6. #16
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    Quote Originally Posted by gavs View Post
    The point being made Greg is that cross drilled rotors are pointless for road going vehicles, regardless of if they're steel or carbon ceramic.
    You seem to have ignored this part.

    Quote Originally Posted by kaanage View Post
    We are talking about braking at levels that shouldn't be experienced on public roads, even by manic heroes. For road use, normal ventilated rotors should be all that is necessary. And I seriously doubt that a properly driven and maintained Polo would experience pad or fluid fade with stock rotors except on a race track.
    Your original post does not differentiate between road and track conditions and context is not irrelevant.

    But IF someone was really at the limits of their brakes capacity and couldn't do the big brake thing for whatever reason, then cross-drilling/slotting will be of some benefit along with the disadvantages already discussed.
    Also, you talk about the possibility of getting lower overall weight with a big brake setup using aluminum top hats but this is pretty unlikely and even with a marginal weight decrease, rotational inertia is likely to increase due to the average diameter increase of the rotor surface.

    And I still don't believe that a car like a Polo Gti should be fading brakes on the road if driven properly. Being "king of the late brakers" on public roads is not responsible behaviour and is totally unnecessary, even for showing off - it's not even smart on a race track except when making a block pass while circuit racing.
    Last edited by kaanage; 25-03-2012 at 09:51 PM.
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  7. #17
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    So how does one change that adaptation code? Sounds like 1 might give better feel than default...?

  8. #18
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    VCDS, I'd imagine.
    Does anyone know if this setting is common for all recent VWs?
    Resident grumpy old fart
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  9. #19
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    Quote Originally Posted by mythik View Post
    Gavs,

    The owner of a 6r polo gti was having some issues with voltage / battery / car not starting and I was taking a look to save the trip to the dealer as I work with them. Turns out it was a faulty battery - temporary battery in place - all fixed.

    Anyway, while I was there, I remembered your 'the pedal isn't connected to the master cylinder'. From where I can stand, the foot pedal is indeed connected to the master cylinder directly, and the pedal itself has electronic position sensing on it but is connected to the main master cylinder which allows the master cylinder vaccum assist level to be adjusted base on the input / module settings.

    Based on your assertion earlier Gavs, if the pedal is not connected in any way to the master cylinder, the experience I should have when no engine is running and no battery is connected is the brakes do not work at all (which would never, ever, ever pass safety standards just fyi).

    So, I removed the battery, drained the system entirely of power and on the top of a hill, rolled down it without any assisting. Low and behold, the first few presses, residual vacuum in the system assisted the brakes once, maybe twice, then it was all up to my to exert/pump the master cyl to apply pressure to the brakes. It wasn't brilliant, but it worked.

    /2c.
    Glad you did, I stand corrected. Makes sense too that it would be, once again, asumptions from reading service manuals has caught me out

    ---------- Post added at 09:10 AM ---------- Previous post was at 08:22 AM ----------

    But IF someone was really at the limits of their brakes capacity and couldn't do the big brake thing for whatever reason, then cross-drilling/slotting will be of some benefit along with the disadvantages already discussed.
    Also, you talk about the possibility of getting lower overall weight with a big brake setup using aluminum top hats but this is pretty unlikely and even with a marginal weight decrease, rotational inertia is likely to increase due to the average diameter increase of the rotor surface.
    Generally, I would agree with you (like i do on a good 90% of things), but when you see this kind of weight saving, per corner at the front.... (courtesy of APR)


    VS



    That is a 4 piston, 323mm alcon setup (shown in one of the previous images) vs the stock, single piston, sliding caliper setup with 288mm rotor.

    And I still don't believe that a car like a Polo Gti should be fading brakes on the road if driven properly. Being "king of the late brakers" on public roads is not responsible behaviour and is totally unnecessary, even for showing off - it's not even smart on a race track except when making a block pass while circuit racing.
    I agree, it is quite stupid, but on the odd occasion when someone might like to drive a bit more spirited, either down mount buller or on a track, there is the possibility of the brakes fading. I personally, would prefer the possibility of the brakes fading to be a slim one, not a certainty, but hey, that is just me. As Scott said, 6 corners and his brakes were shot and I know that Scott can be a bit more brave than others when driving, but I also know he isn't an idiot. Some cars are just under braked (VX-VE Commodore SS for example) from the factory. Is the 6R GTI one of them?.....

    We got the Win for DQ200. Now come to the party VGA on DQ250 and DQ500 issues. You know they're there.
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  10. #20
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    Quote Originally Posted by gavs View Post
    some cars are just under braked (VX-VE Commodore SS for example) from the factory
    This is so you can do FULLY SICK BURNOUTS BRO.

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